Floatation??

[aguaflaca]

that does it
thanks
I had the displacement thing figured out and then confused myself when I started thinking about my boat

[richg99]

Good. Glad that we all could help.

It isn't an easy topic to discuss.

Wait until you stumble across "hull or displacement speed" .... usually discussed when speaking about a sail boat, but the issues affect every "displacement hull" boat. Ha Ha Rich.

p.s. a kayak is normally a "displacement hull" boat.

[gwinyak]

Thanks for the science lesson Rich! That does make sense!
I spend all day in a history classroom, I forget how cool science can be...ha!

As I was reading all of these posts... I was reminded of this....


.......http://www.starch.dk/isi/kroyer/schrooge.asp

[richg99]

Gwin...thanks, GREAT STORY...I have tagged it for future use!

After you reminded me, I did remember the ping pong story from long ago. Let's see...in 1949 I was ten years old. I might have read that comic book!

I'm afraid I don't have the education to be giving any science lessons. I've just owned lots and lots of boats, of all sorts, over 60+ years of enjoying the water.

Rich

[dwilliams35]

It has been said a number of times already......

Adding ANYTHING INSIDE of the hull does nothing for flotation, other than adding a little more weight...which is a negative for flotation.

INSIDE of the hull does not increase the displacement (area touching the water). Displacement is what makes things float. Displacement is a combination of the square inches of area touching the water.... and ....the weight of the object.

Think of it this way....You put a bucket in a pond. It is metal so it weighs something. It floats because the area of displacement is sufficient to hold up its weight. You stuff a balloon into the bucket. does it float higher??? NOPE...

Now, glue/tie that balloon onto the outside of the bucket....you have increased the displacement area (by the area of the balloon touching the water) and it will float higher.

Rich

this makes total sense
but,
why do most boat hulls have foam on the inside?

I'm assuming you're talking about powerboat hulls, not kayaks: they do supply some floatation, since the hull does catch and hold water; however, they're also using it to provide support while they're laying the fiberglass.

[aguaflaca]

It has been said a number of times already......

Adding ANYTHING INSIDE of the hull does nothing for flotation, other than adding a little more weight...which is a negative for flotation.

INSIDE of the hull does not increase the displacement (area touching the water). Displacement is what makes things float. Displacement is a combination of the square inches of area touching the water.... and ....the weight of the object.

Think of it this way....You put a bucket in a pond. It is metal so it weighs something. It floats because the area of displacement is sufficient to hold up its weight. You stuff a balloon into the bucket. does it float higher??? NOPE...

Now, glue/tie that balloon onto the outside of the bucket....you have increased the displacement area (by the area of the balloon touching the water) and it will float higher.

Rich

this makes total sense
but,
why do most boat hulls have foam on the inside?

I'm assuming you're talking about powerboat hulls, not kayaks: they do supply some floatation, since the hull does catch and hold water; however, they're also using it to provide support while they're laying the fiberglass.

I'm not one to argue but rich answered the floatation issue in power boat hulls

what fiberglass does the foam support?
hand laid hulls are built starting from the outside in a reverse mold.
I know for a fact my hull was complete before the foam was sprayed in because I saw it done.

[richg99]

Told you it was a difficult subject to discuss.......

Flotation......

Of course, foam or bottles or air-filled bags float.... better than water.

Of course, kayak and most boat hulls will take on some water. That wasn't the question.

The original question was simple. "If I add more weight to my boat (any boat)...can I offset that weight by stuffing some foam into the same hull."

The answer is simple.....NO....

Stuffing foam inside of a hull will NOT make the hull float any higher. It will help if you take on a lot of water....but....that wasn't the question.

Try it with a bucket in your bathtub....

Rich

[callowayDUDE]

Look what I started haha...

[richg99]

Calloway. Yea, thx. This subject HAS to come up from time to time. Did you read about the 2/3 rds rule?....

[callowayDUDE]

I did... but if I keep to that ratio, I won't be doing any fishing, My yak is rated for 250, and I'm about 175, so that's already about 2/3rds... But I think I'm gonna consider some different mounting options for my TM (that aren't as heavy as a 2X4), and probably move the battery to the bow as to hopefully balance the weight a little better... I'll probably also slim down my onboard gear as well (lighter anchor, less tackle, half a case of beer as opposed to a full case haha) but in the long run I'll just get a yak that can handle the amount of gear I like to bring...

[richg99]

Yea, I suspect a SINK would come out better in that ratio, due to its inherently higher relative side height.

Be careful. An overloaded boat of any type is not a good thing in which to be out in deep water.

Rich

[callowayDUDE]

Be careful. An overloaded boat of any type is not a good thing in which to be out in deep water.

Rich

Thanks, I will definitely do some shallow water testing before I commit to anything

[TG Canoes and Kayaks]

As most kayak manufacturers go, the listed capacity of a kayak is the total weight allowing the watercraft to float, on flatwater, with about 2 - 3 inches of freeboard (the part of the kayak above of the water). Not only is that a dangerously small amount of freeboard in an open kayak (or any kayak for that matter), the kayak will be pushing water out of the way and paddle like a log. That said, we normally take the capacity number and multiply it by 2/3 to get the performance/working capacity. That number is the most weight you put into a kayak while still enjoying the attributes the kayak was designed for. A 300# capacity x 2/3 = a 200# and below working capacity. You can increase weight to the working capacity at the detriment of the performance of the kayak. Never go above the stated capacity, especially with sit-inside kayaks, as they are rain gauges and will take on water by leaning left or right, even using a nylon spray skirt.

That stated, I believe you need a kayak with more capacity. Look for 12' and, preferably, a 14 footer. Performance (speed and tracking) automatically comes with longer kayaks. Generally, long and skinny = fast and tippy, while short and wide = slow and stable. The only way to gain capacity is by increasing length and/or width. Too much width produces drag, however. Although wider increases stability, it drops performance - think raft. A broad range for paddling kayak widths is 27" to 32". The important factor is length offers more capacity and more performance without extra paddling effort on your part. That is of great benefit paddling flatwater. If the tailing Reds are 5 miles away, length will get you there.

Demo as many kayaks as you need to buy the right kayak the first time. Find a dealer willing to make that happen.

[gwinyak]

That stated, I believe you need a kayak with more capacity.

see, now you have good excuse to buy a new kayak! I look for a good excuse to buy a new kayak all the time!

[callowayDUDE]

That stated, I believe you need a kayak with more capacity.

see, now you have good excuse to buy a new kayak! I look for a good excuse to buy a new kayak all the time!

yeah haha, Now if I could only get the wifey to let me spend that kind of cash

[rodandroll]

That stated, I believe you need a kayak with more capacity.

see, now you have good excuse to buy a new kayak! I look for a good excuse to buy a new kayak all the time!

yeah haha, Now if I could only get the wifey to let me spend that kind of cash

Guess you finally figured out I was right all along!! And just as I said, whatever you put inside the hull ADDS WEIGHT!!!!!! - regardless of how much it weighs

[callowayDUDE]

Guess you finally figured out I was right all along!! And just as I said, whatever you put inside the hull ADDS WEIGHT!!!!!! - regardless of how much it weighs

Yeah, I was just looking for more of an explanation...

Thanks though